(a) Field of the Invention
The present invention relates to a plastic packaged semiconductor device comprising a semiconductor element which is plastic-packaged or plastic-sealed.
(b) Description of the Prior Art
An example of the conventional plastic packaged semiconductor device is shown in FIGS. 1(a) and 1(b) as a plan view and a sectional view, respectively. For instance, the plastic packaged semiconductor device of this type comprises, as shown in FIGS. 1(a) and 1(b), a lead frame which comprises an island 3 supported by a rectangular-shaped outer frame through suspension leads 8 in the central portion thereof and a plurality of leads 5 extending from the outer frame and distributed around the periphery of the island 3; a substrate 7 which is bonded onto the island 3 through a silver paste and on which a plurality of distributing wires 4 radially arranged are formed; a semiconductor element 1 bonded onto the substrate 7; bonding wires 2 which connect the distributing wires 4 to input-output terminals of the semiconductor element 1; and bonding wires 2a which connect the distributing wires 4 of the substrate 7 to the leads 5. In addition, the semiconductor element 1 and the circumference thereof are enclosed and embedded in a resin body 6 for plastic-packaging to give a plastic packaged semiconductor device.
Such an assembling technique is likewise applicable to the production of composite type semiconductor devices, for instance, those in which a plurality of semiconductor devices are loaded on a substrate 7.
Recently, there has been advanced the development of small-sized and high speed-operating semiconductor devices equipped with multiple pins. However, it has been difficult to design these conventional plastic packaged semiconductor devices of this type so as to have a thickness as thin as possible and withstand a high operating power source.
For instance, as shown in FIG. 1(b), in the conventional plastic packaged semiconductor devices, a semiconductor element 1 is loaded onto a substrate 7 which is bonded to an island 3, distributing wires on the substrate are then wire-bonded to leads 5 and thereafter the assembly is plastic-packaged. For this reason, the thickness of the package is necessarily increased. Therefore, it is very difficult to reduce the thickness of such a package. In addition, if a substrate 7 formed from a glass-epoxy resin is employed, a semiconductor element having high consumed power cannot be loaded thereon because of the low heat radiation capacity of the glass-epoxy resin. Moreover, the substrate 7 is connected to the leads 5 of the lead frame through wire bonding in the conventional plastic packaged semiconductor devices and, therefore, the time for practicing the wire bonding operation is about two times that observed for semiconductor devices in which each electrode pad serving as input-output terminal of the seminconductor element is wire-bonded to a corresponding lead of a lead frame thereof.